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首页> 外文期刊>Molecular and Cellular Biology >Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.
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Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.

机译：在果蝇的果糖-1,6-双磷酸醛缩酶基因中交替使用古代外显子的不同形式。

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摘要

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.
机译：果蝇的果糖-1,6-二磷酸醛缩酶基因含有进化上保守的3'外显子的三个不同拷贝。编码醛缩酶的两个mRNA含有三个外显子，仅在poly（A）位点不同。第一个外显子很小并且没有编码。第二个编码前332个氨基酸，形成催化结构域，与脊椎动物的第2至8外显子同源。第三个外显子编码最后29个氨基酸，被认为可以控制底物特异性，并且与脊椎动物外显子9同源。第三个mRNA替代另一个3'外显子（4a）替代第3外显子，并编码与醛缩酶非常相似的蛋白质。第四个mRNA从另一个启动子开始，并与醛缩酶信息共享第二个外显子。但是，两个外显子3a和4a一起替代了外显子3。与外显子4a一样，外显子3a与末端醛缩酶外显子同源。外显子3a-4a连接使得外显子4a的翻译框架与产生与醛缩酶相似的蛋白质的框架不同。由第三和第四个mRNA编码的推定蛋白质很可能是醛醇酶，具有改变的底物特异性，说明了重复和发散外显子的交替使用作为适应酶活性的进化机制。

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